Bag A contains 5 white balls and 2 green balls. Bag B contains 3 white balls and 4 green balls. A fair die is rolled and if a 1 or a 2 comes up, a ball is randomly selected from Bag A; however, if a 3, 4, 5 or 6 comes up, a ball is randomly selected from Bag B. a) What is the probability of selecting a white ball? b) If a white ball is selected, what is the probability that this ball came form Bag A? Alright so a) I figured out. It's 11/21. I got that by multiplying the likelihood of first rolling a one or two (2/6) with the likelihood of getting a white ball in bag a (5/7) and then adding that number to this same process in bag b. However for part b), for some reason I just can't wrap my head around it. I know that the probability of selecting a white ball is now 11/21, so is this an equation dealing with P(bag a ("given that" line)white ball probability)? Conditional probability? A little lost.